Niraparib p-toluenesulfonate is the p-toluenesulfonate salt form of niraparib, a potent and selective poly (ADP-ribose) polymerase (PARP) inhibitor. Its chemical name is 2-[4-((3S)-3-piperidinyl)phenyl]-2H-indazole-7-carboxamide 4-methylbenzenesulfonate. The salt form is often used to improve the physicochemical properties, such as solubility and stability, of the active pharmaceutical ingredient (API). Niraparib is a key active pharmaceutical ingredient (API) used in the treatment of specific types of cancer. It is primarily indicated for the maintenance treatment of adult patients with recurrent epithelial ovarian, fallopian tube, or primary peritoneal cancer who are in a complete or partial response to platinum-based chemotherapy. As a PARP inhibitor, niraparib works by blocking the PARP enzyme, which is involved in DNA repair. This mechanism is particularly effective in cancer cells with homologous recombination deficiency (HRD), such as those with BRCA mutations, leading to synthetic lethality and cancer cell death. This specific salt form, niraparib p-toluenesulfonate, is crucial in the pharmaceutical development and manufacturing process. It serves as a key intermediate or reference standard for quality control. In analytical chemistry, it is used as a reference standard or impurity standard to monitor the purity, identity, and stability of the final drug product, ensuring batch-to-batch consistency and compliance with regulatory standards.